Taxonomy and nomenclature of Sphenopteris and allied fossil-genera of Carboniferous seed-plant fronds

Most remains of Carboniferous lyginopteridalean seed-plant fronds used to be classified in a single fossil-genus (Sphenopteris) based mainly on pinnule morphology. By incorporating additional characters linked to frond architecture and rachial features a more natural taxonomy has now been achieved. Eight fossil-genera of lyginopteridalean fronds are now recognised (Sphenopteris, Calymmotheca, Eusphenopteris, Karinopteris, Mariopteris, Palmatopteris, Spathulopteris, Sphenopteridium) for which the diagnostic descriptions, nomenclatural types and stratigraphical/chronological distribution are clarified. This provides a more natural and therefore robust means of recording these fossils, which will help improve studies on past plant diversity and floristics. A by-product of this revision is that some fossil-species of fern fronds previously placed in Sphenopteris will need to be reclassified into fossil-genera that are defined on reproductive structures.